Store.rg-adguard.net is a third-party, widely trusted service that acts as a parser to generate direct download links for application packages from official Microsoft servers. It is primarily used by administrators and power users for offline installation, bypassing store restrictions, and downloading specific versions for archival purposes. For more details, visit Microsoft Q&A Microsoft Learn

The site has (especially on mobile). Pop-ups may say:

If you want any of the following, tell me which and I’ll provide it: